Maybe done by Bish? Anyone remember where the story was written up. The stock was maple and the rear sight hump was machined off.

He made a contoured metal handguard for it

I believe Tommy Bish wrote about it in his book on gunsmithing. I used to have that book but recently sold it

I have the Gun World issues from 1964 but the maple stock was not among the 4 issues, only the walnut one and the wooded case.

I think I know which Gunsmithing book

I have the book and know the article well; but anyone who butchers a WW2 carbine now, is, less than astute. IE, you instantly turn a $1200 rifle into a $400 one.
Tommy Bish cut up a nice Winchester carbine.

buddy's got a receiver and wants to build a Spitfire.

He will be much better off restoring it to military configuration if it is a good condition WW2 receiver.
I will send you the article anyway. If he decides to butcher, please don't tell me.
Just noticed that my book is autographed by Tommy L. Bish.

I've got a modern made Springfield Armory carbine receiver that I'll never use. PM if interested. It'd be much better to use that for a Spitfire than an original USGI receiver. A quick look on GunBroker will tell you what that USGI receiver is worth.